Sony HVL HVL-F56AM Operating Instructions Manual page 88

Adjusting bounce angle
Simultaneously using direct light and bounced light from the flash
produces uneven lighting. Determine the bounce angle with respect to the
distance to the reflective surface, the distance from the camera to the
subject, the focal length of the lens etc.
Correct
Incorrect
When flash is bounced upwards
Determine the angle in relation to the following table.
Bouncing to Left and Right
Rotating the flash by 90° to bounce light sideways is recommended. If an
angle of less than 90° is used, care should be taken to ensure that direct
light from the flash does not illuminate the subject.
26
Focal length of lens
70 mm minimum
28-70 mm
28 mm maximum
Bounce angle
45°
60°
75°, 90°